Ubuntu is way too popular for the ISO to become corrupted and no one notices. At what stage does the error message appear, while you're burning the disc or when you run it? Are you using decent blank CD's? Are you using 32 or 63 bit?

When you run Ubuntu click the icon that says 'Software Centre' and search for whatever you want to install, though  you should get a basic grasp of how computers work before you try projects like this, it always ends in 'Linux sucks because 'insert easy to solve using Google problem here', im not having a go at you just after spending years on Linux forums it amazes me how people don't know search engines exist, thousands of them.